Many types of fuel filters (also referred to as “separators”) are known in the prior art. A popular type of fuel filter has a housing that encloses a replaceable ring-shaped filter element. The filter element ensures that impurities are removed from fuel before it is delivered to system components such as fuel injection pumps and fuel injectors. Mating portions of the housing form an interior enclosure for the element, and the housing portions may be separated for replacement of a spent filter element. Periodic replacement of the filter element is required so that the filter element will not become so loaded with impurities that fuel flow is restricted. Cost and ease of manufacture have been important considerations with such elements. However, problems may arise when such filter elements are replaced.
One problem is that filter elements with different sizes and/or filtration capabilities often have identical mounting configurations and can fit on the same filter head. However, use of the wrong filter can cause poor engine performance and allow undesirable amounts of contaminants to pass through the fuel system.
Another problem is that individuals may remove a spent filter element and simply re-attach the housing portions without a fresh element. While the engine may operate (at least for a short period of time), this can be detrimental to the engine.
A still further problem is that disturbance of the spent element during replacement may cause collected impurities to fall off the element. In some designs, these impurities may pass into the outlet of the filter housing and reach the components downstream in the fuel system.
To reduce and at least partially eliminate these problems, the filter assembly shown in Patent Specification U.S. Pat. No. 4,836,923, owned by the Assignee of the present application, was developed. This filter includes a unique replaceable filter element that is attached to a removable cover. The housing has an internal standpipe with an opening at the top end. When the element is removed from the housing, the fuel level in the housing falls below the opening in the standpipe. As a result, the impurity-laden fuel left in the housing is less likely to reach the outlet. Likewise, when a new element is installed in the housing, only fuel that has been purified by passing through the media of the element is enabled to reach the opening and pass out of the housing.
While this filter design has many advantages, if the filter element is not removed carefully, impurity-laden fuel in the housing or from the outer surface of the element may fall into the opening in the standpipe. If this happens, some impurities may still reach the downstream components of the fuel system.
In addition, the cover is discarded with each spent element. This is undesirable from a conservation and solid waste standpoint. It is generally desirable to minimize the amount of material discarded, particularly if a discarded element must be treated as hazardous waste. The cover also represents a portion of the cost of the replacement element. As a result this design adds cost to the replacement element. Further, the element may be separated from the cover, and the cover re-attached to the housing without a fresh element also being installed. As such, it still does not fully address the problems associated with operating an engine without a filter element installed.
A further improved filter is shown in Patent Specification U.S. Pat. No. 5,770,065, also owned by the assignee of the present application. In this filter, the filter element is received around a standpipe extending centrally in the housing. A spring-biased valve element internal to the standpipe is normally closed, and can be engaged and moved to an open position by a projection on the element when the element is properly installed in the housing. This filter provides the advantages of the '923 patent, as well as prevents impurity-laden fuel from passing through the standpipe when the element is changed. The assembly also prevents operation of the engine without an appropriate element in place.
The filter shown in the '065 patent has received wide-spread acceptance in the marketplace. Nevertheless, it is believed that there exists a need for a still further filter which has the advantages of the '065 patent, but where the valve structure is located exterior to the standpipe. Such a valve structure can be easier to manufacture and assemble, thereby reducing the cost of the assembly. It is also believed there is a demand for a filter where the opening into the standpipe is located toward the lower end of the filter. This can prevent or at least reduce the chance of pulling air into the system, as the opening is kept below the level of the fuel.
As such, it is believed that there exists a need for a further improved fuel filter which overcomes at least some of the above-described drawbacks.
According to one aspect of the present invention there is provided a filter subassembly comprising a filter element including a ring of filter media circumscribing a central axis. The ring has a first end and a second end. First and second end caps are fixed to the first and second ends, respectively, of the filter media. The second end cap has an annular end cap portion sealingly bonded to the second end of the filter media and a valve-actuating portion. The valve-actuating portion includes an axially extending cylindrical portion connected to the annular end cap portion and circumscribing the inner diameter of the annular end cap portion. An annular base is connected to the cylindrical portion and extends radially inward from the cylindrical portion to define a first central opening which can receive a pipe. At least one key is provided with the valve actuating portion having an engaging portion radially inward spaced from the cylindrical portion and axially spaced away from said annular base.